1. Field of Invention
The invention relates to measurement devices and more particularly to a device having a mechanism which allows an individual to determine whether there is a gap variation between a subject object adhered to the device and an object to be sensed by viewing pattern, indicia, or color change through a window thereon.
2. Description of Related Art
Distance (or gap) variation between one member and another member is an important factor of determining whether a potential structural failure exists. Thus, how to precisely measure such variation is a critical issue to be addressed.
Displacement of one component relative to the other component can be found in bridge structures, buildings, etc. For safety purposes, a precise measurement of any displacements should be carried out.
Typical device for sensing gap variations are disadvantageous because they are either insensitive or imprecise when a longitudinal variation is converted into a transverse variation for visual judgment. Thus, the need for improvement still exists.